We do strive to be satisfactory.
The internet connection that is first accessible after rebooting is what your device prioritizes. So if the Pi still recognizes the ethernet in the first seconds before you disconnect it, it CAN lead to an issue. However, this does not happen very often and has become less and less of an issue as we improved and debugged Max2Play over time.
My previous diagnosis is just based on the small information that I can glean from this correspondence and the debug logs. However, the device’s many processes that run concurrently are something I am not privy to, as is your WiFi setup and its complexities. I assume the solution happened due to a process of your router, but the most important thing is, that it works 😉
WPS does not require an additional dongle, we just created the HowTo when the Raspberry Pi 2 was the newest model and it did not have built-in WiFi.